The present invention relates to a method and apparatus for treating a liquid and, more particularly, to a method and apparatus for electrocoagulation of liquids by electrolytic treatment to cause impurities in the liquid to be removed or separable.
It is known in the art to electrolytically treat liquids to allow separation of a broad range of contaminants including metals, solids, pathogens, colloids and other undesirable substances. Electrolytic treatment involves the use of an electrical field which is applied to a liquid contained in a chamber in order to coagulate and otherwise to allow for removal of impurities found in the liquid. One example of a prior art device and method for electrolytic treatment is disclosed in PCT Publication No. WO 9640591. According to this invention, a waste stream is first passed through a polarizing means having an electrical potential that is different than ground potential, and then passed through an electrocoagulation chamber including a plurality of elongate electrodes or electrocoagulation blades which have different electrical potentials in comparison to one another. A plurality of holes are provided in the electrodes to cause turbulence in the waste stream which, in turn, increases the efficiency of the electrocoagulation. Although this device may be adequate for its intended purpose, one disadvantage of this device is that the torturous flow path of the waste stream as it passes through the device requires the electrodes or electrocoagulation blades to be of a high strength to withstand the high water pressure which must be used in order to keep the waste stream from clogging. Because the blades of these devices have to be significant in size and strength, a limited number of them can be used in a specified volume which reduces the actual surface area available for electrocoagulation treatment. Additionally, these coagulation blades require higher input line voltages in order to obtain the desired amperage between the blades in the electrical field because their surface area is limited by the high pressure. Smaller plates can withstand higher pressures, but the ability to maintain a desired amperage is sacrificed because available blade surface area within an electrocoagulation device is directly related to the amperage which can be maintained. Additionally, the torturous path also causes problems due to trapped gases produced by the electrolytic reaction in the chamber which further increases the pressure upon the blades. Accordingly, a high powered pump must be used to overcome the natural tendency of the waste stream to clog within the chamber. This PCT publication encompasses the same subject matter as disclosed in U.S. Pat. No. 5,611,907 to Herbst, et al. and U.S. Pat. No. 5,423,962 to Herbst, and further includes subject matter not found in these other patents.
Other examples of electrolytic treatment devices are disclosed in U.S. Pat. No. 4,293,400 to Liggett and U.S. Pat. No. 4,872,959 to Herbst, et al. These devices utilize electrodes in the form of metal tubes or pipes but require great effort in repairing or replacing the tubes. This amount of down time is unacceptable for many commercial applications.
U.S. Pat. No. 5,043,050 to Herbst discloses flat electrodes used within a coagulation chamber; however, in order for the apparatus of this invention to be used, the edges of the coagulation chamber must be tightly sealed. After long periods of use, the seals are difficult to maintain.
U.S. Pat. No. 3,925,176 to Okert discloses the use of a plurality of electrode plates for electrolytic treatment of liquids. However, these plates are not intended to be removed either as a whole or individually. Furthermore, the device disclosed in this reference cannot be powered in a series electrical connection which is desirable in many circumstances.
U.S. Pat. No. 5,302,273 to Kemmerer discloses an ionic reaction device including a tubular housing with multiple circular electrode plates for the treatment of a fluid. Because of the torturous path utilized in the reaction chamber of this device, high pressures are required to move the liquid through the device, and the device appears susceptible to clogging and excessive gas buildup.
One shortcoming of all of the foregoing prior art references is that there is no means by which to transform the input line voltage to the voltage and amperage necessary to optimize the electrocoagulation treatment without having to use a separate transformer. In other words, the electrocoagulation chambers themselves do not have the capability to transform the input line voltage to a desired voltage and amperage within the electrical field of the electrocoagulation device.
Another shortcoming of the prior art which utilizes a torturous flow path is that the electrodes or electrocoagulation blades require precision holes to be cut to allow gaskets to be bolted between the blades in order to withstand the pressure created by the torturous path. Additionally, the blades have to be laser cut with extreme precision in order to maintain the exact desired path. Deviation from a predetermined path can result in clogging due to buildup of coagulated solids bridging between misaligned blades. These manufacturing requirements greatly add to the cost of building an electrocoagulation device.
Another shortcoming of the prior art, which includes many of those discussed above, is that the blades are not easily removable for replacement or cleaning. Particularly for those chambers utilizing a tortuous path, a great number of bolts and gaskets are required to keep them in alignment. Accordingly, these pieces of hardware must be removed in order to replace the blades.
Each of the foregoing disadvantages are overcome by the apparatus and method of this invention. Additionally, the apparatus and method of this invention achieve other advantages discussed more fully below.
In accordance with one aspect of the present invention, an apparatus for electrocoagulation of liquids is provided. In its simplest form, the device or apparatus includes a housing defining a reaction chamber, and a plurality of spaced reaction plates/blades which are oriented in a vertical position within the reaction chamber. An inlet is provided to allow a desired flow of liquid into the reaction chamber and into the gaps or spaces between the blades. An outlet is provided at an elevation higher than and downstream of the inlet for allowing the liquid to flow from the chamber after the liquid has been treated in the chamber. Selected blades connect to electrical leads which carry an input line voltage. An electrical field is created in the chamber between the electrically connected blades. The electrical leads may be attached to selected blades in order to provide the reaction chamber with the desired voltage and amperage to optimize the electrocoagulation of the particular liquid. The ability to vary voltage and amperage within the electrical field of the chamber can be achieved without the use of a separate transformer. The liquid stream flow is in an upward direction through the reaction chamber in the gaps between the plates/blades. Accordingly, the outlet is positioned at the higher level above the inlet. A pump may be placed upstream of the inlet in order to provide additional head for the flow of liquid passing through the apparatus. A series of prefilters or other preconditioning means may be placed in line with the pump and also upstream of the inlet in order to remove solids or other materials which may otherwise clog the reaction chamber. A control unit rectifies the incoming AC line voltage to a DC voltage. Electrical leads interconnect the blades to the DC voltage made available by the control unit. In addition to rectifying the incoming line voltage, the control unit may incorporate a number of other functions which helps to control the apparatus, such as a means to control the speed of the pump and a voltmeter and ammeter to monitor the conditions within the chamber. However, the control unit does not need a transformer as the electrical connections made with the blades allow the desired voltage and amperage therein to be adjusted, as further discussed below. Additionally, the control unit can be in the form of a programmable logic controller which could not only monitor status condition inputs, but also produce outputs to control the electrocoagulation process. For example, the voltage polarity of the electrical leads extending from the control unit can be reversed based upon a timing sequence controlled by the controller. As a further example, the control unit can measure the flow rate of the liquid stream and adjust it accordingly by either manipulating the pump speed, or adjusting the flow rate through a valve positioned upstream of the inlet. After the liquid stream has been electrolytically treated, the liquid stream may be passed through a development chamber and/or through secondary separation treatment in order to remove the bulk of the contaminants which still remain in the liquid stream. It is the intent of the electrocoagulation device of this invention to remove the bulk of contaminants in secondary separation treatment. Although some contaminants will fall out of the liquid stream to the bottom of the reaction chamber, it is desirable to treat the liquid within the reaction chamber and then by force of the liquid stream, move the contaminants to a downstream secondary separation treatment point. If the bulk of the contaminants were allowed to settle out of the liquid stream within the reaction chamber, then the reaction chamber would have to be cleaned and serviced more frequently. Secondary separation treatment can be achieved with a number of devices placed downstream of the reaction chamber. For example, secondary separation can be accomplished with clarifiers, filters, centrifugal separators, or centrifuges. Each of these devices can be used within secondary separation as referred to herein, and any one or a combination of these devices may be used depending upon the type of liquid stream treated.
In accordance with another aspect of the present invention, a method is provided for electrocoagulation by electrolytically treating a liquid stream. The method may include the steps of passing the liquid stream through a prefilter and pump, and then through the reaction chamber in an upward flow direction. The method further contemplates the steps of passing the liquid stream through an outlet of the reaction chamber and then through a development chamber and/or secondary separation. Additives can be introduced to the liquid stream in order to target the electrocoagulation of a specific contaminant.
The electrocoagulation chambers in all of the embodiments have the ability to transform the power of the rectified incoming line voltage to the voltage and amperage in the electrical field within the reaction chamber to optimize the electrocoagulation treatment. These transforming electrocoagulation chambers therefore allow the same power supply provided to the electrocoagulation chamber to be used over a wide range of the incoming line voltages. Accordingly, a separate transformer is not required which greatly saves in the cost of implementing an electrocoagulation device. Also, the ability to transform the power grid voltage or incoming line voltage enables the invention to be used in many countries which have differing standard power grid or line voltages.
According to another aspect of the invention, the chamber can be operated under a vacuum. By operation under a vacuum, the gas created by the electrocoagulation process will be removed from the chamber faster. Furthermore, the use of a vacuum upon the chamber will reduce the amount of dissolved air within the liquid stream. There are circumstances in which entrained air impedes the electrocoagulation process, depending upon the type of liquid treated and the contaminants to be removed. Additionally, subjecting the liquid stream to vacuum also enables beneficial gases to be dissolved more efficiently in the liquid stream before or after coagulation. For example, if the amount of oxygen dissolved in the liquid stream needs to be increased, the liquid stream can be passed through a vacuum to remove the dissolved air, then oxygen or ozone can be added back to the liquid stream through a venturi. As another example, carbon dioxide could be added to lower the pH of the liquid stream or ammonia can be used in the same way to increase the pH of the liquid stream. Although a vacuum may be utilized, the apparatus can be operated at atmospheric pressure.
Another benefit of operating the chamber under a vacuum is the removal of volatilized gases and compounds which would normally remain in the liquid stream under higher ambient pressure conditions.
According to another aspect of the invention, a vacuum may be applied to the apparatus of this invention by a vacuum hood which is placed over the reaction chamber or, alternatively, the entire reaction chamber may be placed within a sealed container or pressure vessel which communicates with a source of vacuum. If a pressure vessel is used, not only can a vacuum be applied, but the chamber may be kept in a pressurized state. A pressurized reaction chamber would be advantageous in situations in which the apparatus is placed in line with a municipal water source which is already under pressure. Accordingly, no pump or other external pressure means would be required to move the liquid stream through the device.
In another aspect of the invention, the amperage and voltage within the chamber can be adjusted by placing a non-conductive blade or shield between electrically connected blades. Such a non-conductive blade or shield can be made of plastic or PVC and can be removed or added to the chamber in the same manner as the conductive blades. The voltage and amperage within the electrical field may also be modified by adjusting the surface area of an electrically connected blade in contact with the liquid stream. This is achieved simply by raising or lowering an electrically connected blade in the liquid stream. Thus, the amount of blade surface area exposed is directly related to the amperage that will transfer in the electrical field and through the liquid stream.
In another aspect of the invention, turbulence of the liquid stream may be increased by providing a hydrocyclone or diaphragm-type pump upstream of the reaction chamber. Turbulence increases the efficiency of the electrolytic process. Turbulence may also be increased by injecting air into the liquid stream upstream of the inlet of the reaction chamber.
According to a first preferred embodiment, the device of this invention may be configured for use in the home. Alternatively, the size of the first embodiment may be increased to a greater scale in a second embodiment to handle more industrial-type uses which require greater amounts of treated liquid. In a third preferred embodiment, the apparatus of this invention may be modified in a much smaller scale for portable use. In a fourth preferred embodiment, the apparatus of this invention may be incorporated within a pressure vessel which is able to pressurize or depressurize the environment in which the electrolytic treatment takes place. The third embodiment differs from the other embodiments in that no flow occurs through the device. Rather, a static amount of liquid is treated and then removed for consumption.
For each of the embodiments of this invention, the electrocoagulation chambers do not utilize a torturous flow path. The elimination of a torturous flow path of the liquid stream allows thinner blades to be used because the pressure within the chamber is less. The use of thinner blades allows an increased number of blades to be used within a chamber. By increasing the number of blades within the chamber, the surface area of the blades in contact with the liquid stream is increased which enhances the electrolytic treatment of the liquid stream. In other words, the chemical reactions which take place within the chamber occur on the surfaces of the blades; therefore, increasing the number of blades within a set volume ensures that greater electrolytic treatment takes place. Also, because there is no torturous flow path, gases which are produced in the electrolytic process will not create air locks which could otherwise distort the blades and the chamber, and increase the pressure required to pump a constant liquid stream through the chamber. The simple flow path between the blades from the bottom to the top of the chamber allows the gases created by the electrolytic process to rise as bubbles, as a result of their natural buoyancy, which may then freely escape into the atmosphere or be drawn off by a source of vacuum. Also, the bubbles move in the direction of liquid flow which further prevents clogging and reduces the amount of pressure needed to move the liquid through the device.
Because the total surface area of the blades within the chamber is increased, the electrocoagulation unit can be operated at a minimum power consumption. In general, electrocoagulation treatment is dependent on the amperage in the electrical field which is in contact with the liquid stream. If the voltage is maintained within the electrical field at a threshold level greater than 2 volts, the electrolytic reaction will take place wherein metal ions from the blades are added to the liquid stream causing the blades to be consumed over time. Voltage within the electrical field is usually only a concern if it cannot be maintained above the 2-volt level. The total surface area of the blades within the chambers of each of the embodiments is increased sufficiently to maintain the minimum 2-volt threshold while also maintaining the amperage necessary for effective treatment. In other words, the apparatus of this invention can be operated at lower voltages than the prior art which results in reduced power consumption. There is a direct relationship between the voltage which can be maintained in the electrical field for a given amperage based on the available surface area. An increased surface area allows a specified amperage to be maintained at a lower voltage. For example, if 1 amp were required to effect treatment of the liquid and, if the larger surface areas of the blades of this invention allow the 1 amp to be maintained at 2 volts, then the power used is only 2 watts. If a prior art blade having a smaller surface area, say by tenfold, requires a voltage of 20 volts to maintain the 1 amp, then the power consumption would increase to 20 watts. As discussed above, the surface area available in the device of this invention is much greater than many prior art blades. Typically, prior art blades require precision manufacturing and, therefore, are expensive to make. Furthermore, these prior art blades had to be kept at a minimum size in order to withstand pressure within the reaction chamber. Overcoming this size limitation cannot be solved simply by making the blades thicker as this would in turn decrease available blade surface area within the reaction chamber. Making the prior art blades larger or wider without increasing thickness would require less pressure in the reaction chamber which could result in massive clogging or complete flow disruption. Accordingly, the size of such prior art blades had to be kept at a minimum.
The apparatus of this invention is capable of treating many types of liquids to include, without limitation, water, oil and antifreeze.
The foregoing discussed advantages along with others will become apparent from a review of the description which follows in conjunction with the corresponding FIGS.